/*
 * @Author: zxc
 * @Date: 2020-11-25 13:22:03
 * @LastEditTime: 2020-11-25 13:25:13
 * @LastEditors: zxc
 * @Description:合并两个有序链表
 */
/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var mergeTwoLists = function (l1, l2) {
  if (!l1) return l2
  if (!l2) return l1
  if (l1.val < l2.val) {
    l1.next = mergeTwoLists(l1.next, l2)
    return l1
  } else {
    l2.next = mergeTwoLists(l1, l2.next)
    return l2
  }
}
